Surface coatings resistant to chemical warfare liquids



KR 3s05 tab96 United States Patent 3,054,696 SURFACE COATINGS RESISTANT T0 CHEMICAL WARFARE LIQUIDS Leon Segal, Metairie, and Kazuo H. Takemura, New Orleans, La., assignors to the United States of America as represented by the Secretary of the Army No Drawing. Filed June 24, 1957, Ser. No. 667,719 5 Claims. (Cl. 117-72) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to us of any royalty thereon.

This invention relates to surface coatings that render porous materials resistant to wetting or penetration by liquids. In particular this invention provides textiles impregnated with a composite material which renders them resistant to rapid wetting or penetration by chemical warfare liquids without undesirably altering the hand, feel, or air permeability.

Heretofore numerous compositions and treatments for coating the surfaces of textile materials and other air permeable materials to render the materials impermeable to water and similar polar liquids have been developed. Some of these treatments render the treated materials more permeable to organic solvent soluble materials such as oil and the like, and others render the treated materials impermeable to both water and oil. However, the more penetrating chemical warfare liquids have a capability of wetting and penetrating that is many times greater than that of either water or oil. Materials capable of resisting penetration by water and oil are often almost instan taneously penetrated by a liquid such as the warfare liquid designated as GB by the Army Chemical Corps i.e. isopropyl methylphosphonofluoridate. The chemical warfare liquids are polar liquids having a low surface tension. They penetrate a cloth composed of a cellulosic textile material in a fraction of a second regardless of the construction of weave of the cloth.

A primary object of this invention is to provide textiles impregnated with a material which when it is applied to a textile clothing material such as a cotton sateen cloth provides a cloth that is suitable for the usual textile uses and is also sufiiciently impervious to chemical warfare liquids such as liquid GB to protect a person covered by the treated textile and permit him to find shelter and remove drops of the liquid before it penetrates and contacts his body. Another object is to provide a textile impregnant which can be applied to textile fabrics in the field with a minimum of chemical equipment and knowhow, to render the fabrics resistant to chemical warfare agents. A further object is to provide a surface coating capable of covering the surfaces surrounding the interstices of an air permeable porous material to produce an air permeable material which is resistant to wetting and penetration by both polar and non-polar liquids.

The surface coatings provided by this invention comprise: a polymeric surface coating which consists essentially of a polymer formed from copolymerizable molecules at least half of which have the formula where A represents a group of the formula OCOR COOR or CN, R representing a hydrogen atom or a hydrocarbon radical and R representing a hydrocarbon radical; and, bonded to said polymeric surface coating, a Werner-type chromi-nuclear complex in which the acido groups consists essentially of .pertluoroalkanoyl groups containing at least six carbon atoms. The textile materials which are protective against chemical warfare liquids comprise, textile materials impregnated with a com- Patented Sept. 18, 1962 posite material consisting of enough of a polymer of the type defined above to provide a substantially homogeneous polymeric surface coating on the fibers, and, bonded to said polymeric surface coating, a chromi-nuclear complex of the type defined above.

When the above-defined chromi-nuclear complex is bonded to a substantially homogeneous polymeric surface coating of a polymer of the type defined above, the combination in some way exerts a synergistic action in rendering a textile material resistant toward liquid chemical Warfare agents. For example, a cotton sateen impregnated with the polymer only, or a cotton sateen impregnated with the chromi-nuclear complex only, is wetted and penetrated by a drop of liquid GB in a fraction of a second. Yet when the same sateen is impregnated with both of the compositions, in the manner de cribed above, the impregnated sateen may resist wetting and penetration by drops of liquid GB for many hours. In general, a cotton sateen treated in accordance with the present invention will resist wetting and penetration by liquid GB for at least about seconds.

The surface coatings provided by the present invention can be formed upon any material capable of being coated with the specified polymers. The coatings can be formed on ceramic, metal, wood, plastic or the like materials, and can be formed on textile materials composed of vege table, animal, synthetic, or glass fibers.

The polymeric surface coatings can be formed by the usual methods of forming a coating of the specified polymers. For example, the surface coatings can be formed by dissolving or suspending the specified polymers in a relatively volatile inert liquid, wetting the surface of the material to be coated with the solution or suspension and evaporating the volatile liquid. The polymers used can have widely varying molecular weights or degrees of polymerization. The use of rubbery polymers is preferred. In the treatment of textiles, the impregnation of the textile with an aqueous suspension or dispersion of the polymer and the air drying of the impregnated textile is preferred.

Illustrative examples of suitable polymers include polyesters such as polymerized methyl, ethyl, butyl, and the like esters of acrylic acid, the analogous polymerized esters of methacrylic acid; polyvinyl acetate, polyvinyl butyrate, and the like polymerized unsaturated esters of saturated acids; polyacrylonitrile, and the like polymers of unsaturated nitriles; and copolymers of mixtures of such unsaturated esters and unsaturated nitriles containing up to about 50 percent by weight of a copolymerizable unsaturated hydrocarbon, such as the butadienes, ethylene and its homologues and analogues, and the like polymerizable unsaturated hydrocarbons. The use of aqueous suspensions of one or more 2-to-4 carbon atom alltanol esters of acrylic acid; or copolymers of a mixture of acrylonitrile and from about 1.5 to 2 parts by weight of 1,3-butadiene, is preferred. The polymers can be em ployed in the form of those of the film-forming aqueous suspensions of the polymers of the above-defined type which are commercially available under the trade names Hycars, Polycos, Rhoplexes, Darex, Vinylite dispersions, Cehmigum latices, and the like. The aqueous suspensions can contain the usual wetting and/ or emulsifying or dispersing agents in the usual proportions.

The amount of polymer employed to form the polymeric surface coating should be at least enough to form a substantially homogeneous coating. In the case of tex tiles and the like air permeable materials, the amount employed is preferably less than enough to render the material impermeable to air. In the case of a cloth having a porosity comparable to that of cotton sateen, the amount of polymer is preferably from about 20 to 30 parts of dry polymer per 100 parts of cloth.

Werner-type chromi-nuclear complexes in which the acido groups consist essentially of perlluoroalkanoyl groups are known compounds. Processes of producing them and bonding them to the surfaces of a wide variety of materials are described in British Patent No. 712,784, published July 28, 1954. These complexes are also periluoroalkanoyl analogs of the complexes described in US. Patents Nos. 2,373,040, and 2,544,666. They can be pro duced and applied by procedures analogous to the procedures described in the latter patents. In general, the perfiuoroalkanoyl chromi-nuclear complexes can be prepared by effecting contact in solution between the perfiuoroalltanoic acid and a basic trivalent chromium salt of a mono basic acid, which salt has a basicity of not more than 50 percent. They can be bonded to the surfaces of materials simply by forming a film of a liquid containing them on the material. The complexes can be dissolved in organic solvents such as isopropanol and the like alcohols. Illustrative examples of acids suitable for employment as the acido groups of the complexes include: perlluorohexanoic, perfluorooetanoic, perfiuorodecanoic, perfiuorcoctadecanoie and the like acids. The compleses in which the acido groups consist essentially of pertluoroalkanoyl groups containing from about 8 to carbon atoms are preferred.

Where a textile material is being treated the chrominuclear complexes are preferably applied in the form of a water-soluble alkanol solution having a pH between about 2.5 and the pH at which the complex tends to precipitate. The use of the commercially available isopropanol solution which contains about percent by weight of the pertluorooctanoic acid chromicomplcx and is avail able under the trade name I O-Q04 diluted to a solids content of about 1.5 percent, by the addition of water, and adjusted to a pH of at least 4.3 by the addition of a water miscible base, is particularly preferred.

The following examples are illustrative of the details of at least one method of practicing the invention.

Example 1 A polyethyl acrylate emulsion of approximately 30% total solids Was prepared from 50 g. of inhibitor-free ethyl acrylate using 0.01 of potassium persulfate as catalyst, 1.33 g. of dispersing agent (Tergitol Penetrant No. 4), and 100 ml. of distilled water. The components were stirred slowly while being brought to refiux temperature, then heat was removed for from 10-15 minutes, during grade for about 60 minutes, after which it was given a brief wash with a dilute solution of a synthetic detergent and a water-Wash, then air-dried. Times required for wetting and penetration by a drop of liquid GB were in the ranges of 750 to 2600 and 400 to 1170 seconds, respectively. As used in this specification, the terms "wetting time and penetration time have the follow ing meanings. Wetting time is the time required for a drop of liquid, placed on the upper side of the fabric, to dissipate, i.e. to completely lose its identity as a drop. Penetration time is the time required for the underside of the fabric to show the first trace of penetration by a drop of liquid placed on its upper side.

Wetting and penetration by other chemical warfare agents such as I-lD (2,2-dichlorodiethyl sulfide), HN-3 (2,2,2" trichlorotriethylamine), GA (ethyl dimethylphosphoroamidocyanidate), and GP (cyclohexyl methylphosphonofiuoridate), required very long times.

When a commercially available polyethylacrylate emulsion (Hycar 4501 of about total solids) was diluted to about 25% total solids and used in place of the above polymer emulsion, the treated fabrics exhibited wetting and penetration times toward liquid GB in the ranges of 5000 to 15,000 and 1000 to 6000 seconds, respectively. Repellency towards the other agents given above was also increased. The air permeabilities of the repellent fabrics Were hardly different from those of the untreated fabrics.

Example 2 Samples of an 8.5 oz. cotton sateen were coated with a polymeric surface coating by wetting the samples, to a dry pick-up of about 25 percent, with the below-indicated aqueous emulsions of the indicated polymers, some of which are commercially available under the indicated trade names, and air-drying the wet cloth.

A perfluorooctanoic acid Werner'type chromi-nuclear complex was bonded to the polymeric surface coating by immersing the coated cloths in a water-diluted partially neutralized solution of the isopropanol solution, 30% solids, consists essentially of the complex and is commercially available under the trade name 1 0-804, and heating the wet cloths at about 105 centigrade for about minutes in a dehydrative atmosphere. The times required for wettng and penetration by a drop of liquid GB are recorded in the following table. Air-permeability of the cloth was hardly affected by the treatments.

Dry Piek- Up Wetting Penetration Commercial Name Polymer Type of Time, Time,

Polymer, Seconds Seconds Percent 1. Rhoplex ACE-33..- Principally Polyethyl Acrylatc 26-28 3,0000, 500 1, 600%, 000 2. llycar 4500 X 10 31 500-1, 180400 3 I ah. prep 38 850 750 4 Lab. prep 1 Polyvinyl Acetate 3 3,000 400 Hycar 1551 Aerylonitrilebutadieno e0polyrner 25 34 4,000-8, 800 1,750-5, 500 G. Ilycar 1561 do 2l-32 2.000% 400 1,4000, 200

1 Not obtained commercially, prepared in laboratory.

the exothermic initial polymerization reaction. this, the emulsion was refluxed for 1 /2 hours. Remaining monomer was removed by low vacuum distillation.

Unscoured 8.5 oz. cotton sateen was dipped into this emulsion, which was adjusted to 25% total solids, and padded to 100% wet pick-up and air-dried. The dry impregnated fabric having about a 25% weight gain was then dipped at room temperature into a solution of perfiuorooctanoic acid chrom-nuclear complex prepared in the following manner. Five grams of the commercially available isopropanol solution (PC-804) of 30% total solids was diluted at room temperature with 88 grams of distilled water and 7 grams of a 10% hexamethylene tetramine solution in water. The final solution had a total solids content of 1.5% and a pH of 4.4.

The fabric was cured at a temperature of centi- After 60 We claim:

1. A cotton sateen cloth which is protective against liquid chemical warfare agents, comprising: a cotton sateen cloth impregnated with a composite material consisting of from 20 to 30 percent by weight based on the cloth poly ethyl acrylate to provide a substantially homogeneous polymeric surface coating on the fiber surfaces without rendering said cloth impermeable to air; and. bonded to said polymeric surface coating, 21 Werner-type chromi-nuclear complex in which the acido groups consist essentially of perfiuoroalltanoyl groups containing from six to eighteen carbon atoms.

2. An article of manufacture consisting of a textile having a polymeric surface coating consisting essentially of a rubbery polymer selected from the group consisting of polymers of 2-to-4 carbon atom alkanol esters of acrylis acid, 2-to-4 carbon atom alkanol esters of methacrylic acid, polyvinyl esters of fatty acids having two to four carbon atoms, polyacrylonitrile, and copolymers of the above-named compounds with hydrocarbons selected from the group consisting of l,3butadiene and ethylene, and bonded to the exterior of said surface coating a Werner-type chromi-nuclear complex in which the acido group consists essentially of perfluoroalkanoyl acids containing from six to eighteen carbon atoms.

3. A process for producing a surface coating which is resistant to chemical warfare liquids comprising applying to a surface a coating of an aqueous emulsion of a polymer selected from the group consisting of polymers of 2-to-4 carbon atom esters of acrylic acid, 2-to-4 carbon atom esters of methacrylic acid, polyvinyl esters of fatty acids having two to four carbon atoms, polyacrylonitrile and copolymers of the above compounds with hydrocarbons selected from the group consisting of 1,3-b-utadiene and ethylene, allowing said surface to dry, and then applying to said surface a solution containing a Wernertype chromi-nuclear complex in which the acido group consists essentially of perfluoroalkanyol acids containing from six to eighteen carbon atoms, and a Water-soluble base, said solution having a pH of at least 4.3, and again drying said surface.

4. A textile material which is protective against liquid chemical warfare agents comprising a textile fabric impregnated with sufficient rubbery polymer to form a substantially homogeneous coating on the fiber surfaces but insuflicient to render said fabric impermeable to air, said rubbery polymer being selected from the group consisting of polymers of 2-to-4 carbon atom alkanol esters of acrylic acid, 2-to-4 carbon atom alkanol esters of methacrylic acid, polymer esters of fatty acids having from tWo to four carbon atoms, polyacrylonitrile, and copolymers of the above named compounds with hydrocarbons selected from the group consisting of 1,3-butadiene and ethylene, and bonded to the exterior of said polymer a Werner-type chromi-nuclear complex in which the acido groups consist essentially of perfluoroalkanoyl acids containing from six to eighteen carbon atoms.

'5. A method of preparing a cloth which is permeable to air but protective against chemical warfare liquids comprising; dipping cotton sateen in an aqueous p lyethylacrylate emulsion containing about 25% by weight total solids, padding said fabric to about Wet pickup, drying said fabric, then dipping said fabric in an aqueous solution formed of five parts of an isopropanol solution containing 30% by Weight of perfl'uorooctanoic acid chromi-n-uclear complex, 7 parts of a 10% aqueous solution of hexamethylene tetramine and 88 parts of water, said solution having a total solids content of 1.5% and a pH of 4.4 and curing said fabric at a temperature of about C.

References Cited in the file of this patent UNITED STATES PATENTS 2,544,666 Goebel et al. Mar. 13, 1951 2,544,667 Goebel et al. Mar. 13, 1951 2,662,835 [Reid Dec. 15, 1953 2,693,458 Olson Nov. 2, 1954 

1. A COTTON SATEEN CLOTH WHICH IS PROTECTIVE AGAINST LIQUID CHEMICAL WARFARE AGENTS, COMPRISING: A COTTON SATEEN CLOTH IMPREGNATED WITH A COMPOSITE MATERIAL CONSISTING OF FROM 20 TO 30 PERCENT BY WEIGHT BASED ON THE CLOTH POLY ETHYL ACRYLATE TO PROVIDE A SUBSTANTIALLY HOMOGENEOUS POLYMERIC SURFACE COATING ON THE FIBER SURFACES WITHOUT RENDERING SAID CLOTH IMPERMEABLE TO AIR; AND, BONDED TO SAID POLYMERIC SURFACE COATING, A WERNER-TYPE CHROMI-NUCLEAR COMPLEX IN WHICH THE ACIDO GROUPS CONSIST ESSENTIALLY OF PERFLUOROALKANOYL GROUPS CONTAINING FROM SIX TO EIGHTEEN CARBON ATOMS. 